Latest Secure Microcomputers for Smart Cards Have a Power-efficient New 16-Bit CPU that Delivers a Five-fold Improvement in Processing Performance

As consumers become more familiar with the convenience and safety offered by the Smart cards being used worldwide for financial transactions, the handy cards are growing in popularity. The cards are powered by "secure microcomputers," a type of device that Renesas has manufactured for over a decade. Until recently Renesas has supplied three different series of products for Smart cards: the low-end 16-bit AE-3 series chips, mid-range 16-bit AE-4 series devices, and high-end 32-bit AE-5 products (see technology roadmap, Figure 1). Now, though, we are expanding our capabilities in this area.

The primary application for our mainstream AE-4 series secure microcomputers is subscriber identification modules (SIMs) for GSM mobile phones. The chips, based on an AE-4 CPU core, are also used in multi-application cards, financial cards (credit and debit cards, etc.), personal identification cards (ID cards), and public transport cards (ETC cards). Among the internal peripheral circuits provided by standard AE-4 series chips are an encryption co-processor that supports DES (Data Encryption Standard), memory (EEPROM, ROM, and RAM), two I/O ports, a random-number generator, and a watchdog timer. Other internal peripheral circuits available in the series include a modular multiplication coprocessor (MMC), firewall management unit (FMU), ISO/IEC 7816-3 compliant UART, 16-bit interval timer (TMR), and clock multiplier circuit (PLL). A "dual-way series" AE-4 device (contact/contactless) is under development that will incorporate the RF interface needed for contactless Smart cards.

All Renesas AE-3, AE-4 and AE-5 series secure microcomputers share a compatible instruction set. Devices in the AE-4 series are upwardly compatible with those in the AE-3 series, and the products in the AE-5 series are upwardly compatible with those in the AE-4 series. This compatibility allows software developed for one series of chips to be easily reused across the others.

Building on our extensive experience with AE-series microcomputers ― and working to meet the evolving requirements of global Smart card markets ― Renesas is now introducing a new software-compatible series of secure microcomputers: the RS-4 series (see photograph). Simultaneously, we have adopted "RSecure" as the generic name for our secure solutions, and are re-branding our existing range of secure microcomputers under the "RS series" badge. The models in the RS-4 series are the first products utilizing the new nomenclature. A sample emulator containing a "virtual" RS-4 chip is now available, and samples of the secure microcomputers are scheduled for shipment in the second quarter of 2008.

The products in the RS-4 series do much more than introduce a brand name, however. They are built with the innovative (Renesas-proprietary) 16-bit RS-4 CPU, a CISC-type design that delivers five times the processing performance of the AE-4 CPU. In fact, the high level of performance that the RS-4 CPU provides approaches that of our current 32-bit AE-5 CPU, giving the new microcomputers excellent cost-performance ratios.

Devices in the RS-4 series have a maximum operating frequency of 20MHz or 33MHz, depending on version ― two or more than three times faster than the 10MHz maximum of the AE-4 CPU core. Yet the RS-4 core dissipates less power than that older core. One key to its speed and efficiency is the fact that it can execute an instruction in as little as one cycle, whereas the AE-4 core requires at least two clock cycles for this task. Despite the differences between the CPUs, the compatibility of the RS-4's instruction set makes it extremely easy to port software written for AE-4 series devices to the new series of secure microcomputers.

Applications for RS-4 devices are largely the same as those for AE-4 series chips, but the capabilities they offer are enhanced. RS-4 series chips offer improved encryption processing functions for implementing security features that are more sophisticated and robust. Standard on-chip functions include a triple DES co-processor and MMC, for example, and future RS-4 models will incorporate an encryption co-processor that supports the Advanced Encryption Standard (AES).

Obviously, the new microcomputers also take advantage of the latest advances in security technology, such as an internal pseudo-random number generator and effective measures for protecting the chips against optical attacks ― attacks in which a laser is focused on the silicon to induce improper operation. Renesas aims to obtain a 5+ evaluation assurance level (EAL 5+) for RS-4 chips under the Common Criteria international standard for security evaluation. This is the maximum level attainable by an Smart card microcomputer.

To meet the opportunities presented by the remarkable growth of contactless Smart cards like those used in railway and bus ticket gates, Renesas is working actively to add contactless support to the RS-4 series products. Our development efforts in this area are exploiting the advantages of the new 16-bit microcomputers ― particularly the chips' low power consumption, because power efficiency is very important for contactless cards. Looking further into the future, we plan to bolster the RS-4 product line with additional models of secure microcomputers optimized for all types of Smart card applications: contact, contactless, and dual-way types, as shown in the technology roadmap.